Answer
$$10804 \space revolutions $$
Work Step by Step
1. Find the total travel distance in inches.
63360 in. = 1 mi
The car is traveling at 60 mi/h for half an hour:
$$\frac{60 \space mi}{h} \times \frac{h}{2} = 30 \space mi$$
To convert miles to inches, we must multiply it by $\frac{63360 \space in.}{1 \space mi}$
$$30 \space mi \times \frac{63360 \space in.}{1 \space mi} = 1900800 \space in.$$
2. Calculate the total angle (in radians) that the car wheel rotates in 1900800 in.
$s = r\theta \longrightarrow \theta = \frac{s}{r}$
$$\theta = \frac{1900800 \space in.}{28 \space in.} \approx 67885.7$$
3. Convert the angle to number of revolutions:
$1 \space rev. = 2\pi $
$$67885.7 \times \frac{1 \space rev.}{2\pi} \approx 10804 \space rev. $$
